#include <stdio.h>

void str_cat(char s[], char t[]);

int main()
{
    char s[] = "saint";
    printf("%s\n", s);

    str_cat(s, "-");
    printf("%s\n", s);

    str_cat(s, "yellow");
    printf("%s\n", s);

    return 0;
}

void str_cat(char s[], char t[])
{
    int i, j;

    i = j = 0;
    while (s[i] != '\0')
    {
        i++;
    }
    while ((s[i++] = t[j++]) != '\0')
    {
        ;
    }
}